Sealing structure for terminal posts of batteries

ABSTRACT

A battery, particularly of the lead acid type, has two terminals ( 4 ), one connected to the positive plates and the other to the negative plates. Each terminal ( 4 ) is located in an aperture in the battery lid ( 2 ) and a seal ( 10 ) located under the lid ( 2 ) surrounds the respective terminal ( 4 ). A space is also defined around each terminal and contains settable material such as epoxy resin cement in a set condition.

FIELD OF THE INVENTION

This invention relates to a battery, particularly but not exclusively ofthe lead acid type.

BACKGROUND OF THE INVENTION

In a known battery construction the positive and negative platesrespectively are electrically connected together and respectively topositive and negative terminals by means of connecting straps. Theplates are positioned in a box-like container, usually of mouldedplastics material, and a lid is placed on top of the box, the terminalsprojecting through respective apertures in the lid. The lid is sealed tothe box using a suitable cement or by heat-sealing and the terminals aresealed within the respective apertures to prevent unwanted leakage offluid e.g. acid, fumes or gases such as hydrogen

It is also known to use a settable material such as an epoxy resin toseal the terminals in their respective apertures, but neverthelessleakages can and do occur.

SUMMARY OF THE INVENTION

It an object of the present invention to provide an improvedconstruction which does not suffer from or suffers less from thisdisadvantage.

In accordance with the invention a battery comprises positive andnegative plates, two connecting straps, one connected to the positiveplates and the other to the negative plates, the plates and straps beingenclosed in a box with a lid, two terminals, each one projecting from arespective connecting strap through a respective aperture in the lid,two zones on the underside of the lid each one surrounding one of thetwo apertures and facing an upper surface of the respective strap, twocompressible seals, each one surrounding a respective aperture and beingcompressibly located between the respective zone and the facing uppersurface of the strap, and two spaces, each one being defined around arespective terminal interiorly of the respective aperture, each spacecontaining settable material in a set condition.

Preferably each seal, which may be a sealing ring, is compressed by apredetermined amount and may be retained within a groove which surroundsthe respective aperture. The groove may have an overall predetermineddepth less than the height of the seal and may be formed either whollyin the zone or wholly in the upper surface of the strap, or partly inthe zone and partly in the upper surface of the strap. When the zone isin contact with the upper surface of the strap, the seal is compressedfrom its natural height to a height equal to the depth of the groove.The amount of compression is thereby predetermined.

Preferably retaining means is provided for each terminal to ensure thatthe upper surface of the respective strap and the respective zone remainin contact and that the compression of the seal is maintained. Theretaining means may comprise a screw-threaded collar positioned on anexternally screw-threaded portion of the respective terminal, a lowerpart of the collar contacting a region of the lid above theaforementioned zone.

At least one channel may be provided for enabling settable material tobe fed to the space around each terminal, especially when the retainingmeans is maintaining the compression of the seal. The channel may beprovided in the retaining means and/or in the lid.

The apertures may each be positioned at the base of a respective recessformed in the lid and the retaining means e.g. the collar is positionedwholly within the recess. Settable material may surround the retainingmeans.

Each terminal may have a lower part which is embedded in the material ofthe respective strap, the lower part comprising a flanged base portionand a narrower neck portion above the base portion.

BRIEF DESCRIPTION OF THE FIGURES

One embodiment of the invention will now be described by way of exampleonly with reference to the accompanying drawings of which:

FIG. 1 shows a cross-section through part of a lead acid battery inaccordance with the invention;

FIG. 2 shows a similar view to FIG. 1 but the side view of the terminal,collar and upper part of the strap being shown; and

FIG. 3 shows a sectional view on line III—III of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The battery according to the invention comprises a box 1 containingpositive and negative plates (not shown) and a lid 2 secured to the boxby a suitable bonding agent such as an epoxy resin cement. Alternativelythe lid may be secured to the box by heat sealing.

The positive and negative plates respectively are connected by means oflead connecting straps 3. These are formed in a conventional manner bycasting so that lugs on the corners of the plates (not shown) and alower part of a plated terminal 4 are embedded within the respectivestrap 3.

The lid 2 is shaped to have two recesses 5, at the base 6 of each ofwhich is an aperture through which one of the terminals 4 protrudes.Underneath the base 6 is a zone comprising a horizontal surface 7 whichcontacts an upper horizontal surface 8 of the strap 3. Formed within thezone at the base of the recess is an annular groove 9 having a generallyrectangular cross-section which encircles the aperture. A seal in theform of a generally square cross-sectional elastomeric sealing ring 10which has a natural height more than the depth of the groove 9 iscompressed and retained within the groove 9 by contact with the uppersurface 8 of the strap 3. By making the depth of the groove 9 apredetermined amount less than the natural height of the ring 10, theamount of compression of the sealing ring is predetermined andcontrolled.

The terminal 4, machined from a copper alloy such as brass, has ahexagonal flange 11 at its base, and immediately above the flange, aneck portion 12. Lead from the strap 3 enters and fills the neck portion12 during casting so that the terminal 4 is securely located. Theterminal 4 is generally cylindrical, part of the outer surface beingformed with a screw thread 13. Extending part of the way inside and fromthe top of the terminal 22 is an internally screw-threaded bore 14 forreceiving a cable end (not shown).

An internally threaded collar 15 of moulded plastics material such asABS is located on the terminal 4. The lower part 16 of the collar has asmooth outer surface and is wider than the remainder. The under surface17 of the collar contacts the upper surface 18 of the base 6 of therecess 5 encircling the terminal aperture and by tightening the collar15 the zone 7 of the base correctly engages the upper surface 8 of thestrap 3 and the seal 10 is compressed by the required amount. Shortradially extending channels 25 are provided on the underside 17 of thecollar 16 enabling settable epoxy resin to be poured into the recess 5and flow into the space below the collar 16 surrounding the terminal 4above the upper surface of the strap 3 to form a ring 26, which isallowed to set. Channels (not shown) may alternatively or additionallybe formed in the upper surface 18 of the base 6.

The collar 15 has a central part 19 immediately above the lower part 16which is formed with vertical ribs 20 to enable the collar 15 to begripped firmly and tightened or loosened as required. Above the centralpart 19 is an upper portion 21 having an undercut shoulder 23 encirclingthe collar. This retains a separate cap 27 which has a top part 28 and acylindrical part 24 which covers the top of the collar, the cylindricalpart having an inwardly-projecting lip 29 which engages the undercutshoulder 23 In a snap-fit arrangement. The top part 28 covers the recess5, which is part filled with epoxy resin, but has a central aperturethrough which the top 22 of the terminal projects slightly.

When assembling the battery seals 10 are each placed in a respectivegroove 9, one for each terminal 4. The edges of the lid are covered in asuitable bonding agent e.g. epoxy resin and the lid lowered on to thebox with each terminal projecting through its respective aperture in thebase of a recess. A collar 16 is placed on to each terminal and screweddown tightly, causing the seal 10 to be compressed and the undersurfacezone 7 of the base to firmly contact the upper surface of the strap.Epoxy resin is then poured into the recess. Some flows down the side ofthe collar, through the grooves 25 on its under surface and to fill thespace between the inner side of the aperture and the outer side of theterminal. This is shown at 26 in the drawings.

The ring of resin so formed adheres to the lower part of the terminal,to the strap and to the lid to provide a secondary seal i.e. a safeguardif the elastomeric seal 10 falls. The adhesion of the resin to the lead(of the strap and terminal) and the ABS (of the lid) forms an effectivebarrier against acid transport, hence limiting corrosion.

Enough resin is poured into the recess to reach a height approximatelylevel with the top of the collar. When the resin is set, the collar iseffectively locked in position on the terminal. The cap 27 is thenplaced on the collar to cover the recess 5.

This construction provides for reduced terminal corrosion and highersealing integrity, thus leading to longer battery life.

What is claimed is:
 1. A battery comprising positive and negativeplates, two connecting straps (3), one connected to the positive platesand the other to the negative plates, the plates and straps (3) beingenclosed in a box (1) with a lid (2), and two terminals (4), each oneprojecting from a respective connecting strap (3) through a respectiveaperture in the lid (2), characterised by further comprising two zones(7) on the underside of the lid (2), each one surrounding one of the twoapertures and facing an upper surface (8) of the respective strap (3),two compressible seals (10) each one surrounding a respective apertureand being compressibly located between the respective zone (7) and thefacing upper surface (8) of the strap (3), and two spaces each one beingdefined around a respective terminal interiorly of the respectiveaperture, each space containing settable material in a set condition,wherein each seal is contained within a groove that surrounds therespective aperture, and wherein the groove is formed wholly in theupper surface of the strap.
 2. A battery according to claim 1characterised in that each seal (10) comprises a sealing ring.
 3. Abattery according to claim 1 characterised in that each seal (10) iscompressed by a predetermined amount.
 4. A battery according to claim 1characterised in that the groove (9) has an overall predetermined depthless than the height of the seal (10).
 5. A battery according to claim 1characterised in that the groove (9) is formed wholly in the zone (7).6. A battery according to claim 1 characterised by comprising at leastone channel (25) for enabling settable material to be fed to the spacearound the respective terminal.
 7. A battery according to claim 6characterised in that at least one channel (25) is provided by theretaining means.
 8. A battery according to claim 6 characterised in thatat least one channel (25) is provided by the lid (2).
 9. A batteryaccording to claim 1 characterised in that the apertures are eachpositioned at the base (6) of a respective recess (5) formed in the lid(2) and the retaining means (15) is positioned wholly within the recess(15).
 10. A battery according to claim 1 characterised in that settablematerial surrounds the retaining means (15).
 11. A battery according toclaim 1 characterised in that each terminal (4) has a lower part whichis embedded in the material of the respective strap (3), the lower partcomprising a flanged base portion (11) and a narrower neck portion (12)above the base portion (11).
 12. A battery according to claim 9characterised by a cap comprising a top part covering the recess in thelid and a cylindrical part covering the top of the retaining means. 13.A battery according to claim 12 characterised in that the upper portionof each retaining means is provided with an undercut shoulder whichengages with an inwardly projecting lip provided in the cylindrical partof the cap to secure the cap in a snap fit arrangement.
 14. A batterycomprising positive and negative plates, two connecting straps (3), oneconnected to the positive plates and the other to the negative plates,the plates and straps (3) being enclosed in a box (1) with a lid (2),and two terminals (4), each one projecting from a respective connectingstrap (3) through a respective aperture in the lid (2), characterised byfurther comprising two zones (7) on the underside of the lid (2), eachone surrounding one of the two apertures and facing an upper surface (8)of the respective strap (3), two compressible seals (10) each onesurrounding a respective aperture and being compressibly located betweenthe respective zone (7) and the facing upper surface (8) of the strap(3), and two spaces each one being defined around a respective terminalinteriorly of the respective aperture, each space containing settablematerial in a set condition, wherein each seal is contained within agroove which surrounds the respective aperture, and the groove is formedpartly in the zone and partly in the upper surface of the strap.
 15. Abattery according to claim 14, characterized in that each seal comprisesa sealing ring.
 16. A battery according to claim 14, characterized inthat each of the apertures is positioned in the base of a respectiverecess formed in the lid, further comprising retaining means for eachterminal that ensures that the upper surface of the respective strap andthe respective zone remain in contact and that the compression of theseal is maintained, the retaining means being positioned wholly withinthe recess.
 17. A battery comprising positive and negative plates, twoconnecting straps (3), one connected to the positive plates and theother to the negative plates, the plates and straps (3) being enclosedin a box (1) with a lid (2), and two terminals (4), each one projectingfrom a respective connecting strap (3) through a respective aperture inthe lid (2), characterised by further comprising two zones (7) on theunderside of the lid (2), each one surrounding one of the two aperturesand facing an upper surface (8) of the respective strap (3), twocompressible seals (10) each one surrounding a respective aperture andbeing compressibly located between the respective zone (7) and thefacing upper surface (8) of the strap (3), and two spaces each one beingdefined around a respective terminal interiorly of the respectiveaperture, each space containing settable material in a set condition,and further comprising retaining means for each terminal which ensuresthat the upper surface of the respective strap and the respective zoneremain in contact and that the compression of the seal is maintained,and wherein the retaining means comprises a screw-threaded collarpositioned on an externally screw-threaded portion of the respectiveterminal, a lower part of the collar contacting a region of the lidabove the zone.
 18. A battery according to claim 17, characterized inthat each seal comprises a sealing ring.
 19. A battery according toclaim 17, characterized in that each of the apertures is positioned inthe base of a respective recess formed in the lid, and each collar ispositioned wholly within the recess.
 20. A battery comprising positiveand negative plates, two connecting straps (3), one connected to thepositive plates and the other to the negative plates, the plates andstraps (3) being enclosed in a box (1) with a lid (2), and two terminals(4), each one projecting from a respective connecting strap (3) througha respective aperture in the lid (2), characterised by furthercomprising two zones (7) on the underside of the lid (2), each onesurrounding one of the two apertures and facing an upper surface (8) ofthe respective strap (3), two compressible seals (10) each onesurrounding a respective aperture and being compressibly located betweenthe respective zone (7) and the facing upper surface (8) of the strap(3), and two spaces each one being defined around a respective terminalinteriorly of the respective aperture, each space containing settablematerial in a set condition, wherein each of the spaces is separatedfrom its respective seal by a wall extending between a zone (7) and thefacing upper surface of the strap (3).
 21. A battery according to claim20, wherein the wall is unitarily formed with the lid.
 22. A batteryaccording to claim 20, characterized in that each seal comprises asealing ring.
 23. A battery according to claim 20, characterized in thateach of the apertures is positioned in the base of a respective recessformed in the lid, further comprising retaining means for each terminalthat ensures that the upper surface of the respective strap and therespective zone remain in contact and that the compression of the sealis maintained, the retaining means being positioned wholly within therecess.
 24. A battery according to claim 20, characterized in that eachseal is contained within a groove which surrounds the respectiveaperture and is positioned radially outwardly from the wall.
 25. Abattery according to claim 24, characterized in that the groove isformed wholly in the zone formed in the underside of the lid.
 26. Abattery comprising positive and negative plates, two connecting straps(3), one connected to the positive plates and the other to the negativeplates, the plates and straps (3) being enclosed in a box (1) with a lid(2), and two terminals (4), each one projecting from a respectiveconnecting strap (3) through a respective aperture in the lid (2),characterised by further comprising two zones (7) on the underside ofthe lid (2), each one surrounding one of the two apertures and facing anupper surface (8) of the respective strap (3), two compressible seals(10) each one surrounding a respective aperture and being compressiblylocated between the respective zone (7) and the facing upper surface (8)of the strap (3), and two spaces each one being defined around arespective terminal interiorly of the respective aperture, each spacecontaining settable material in a set condition, wherein compression ofthe seal is provided by a collar that is attached to a respectiveterminal, each collar including channels that provide fluidcommunication between a respective space and a volume located radiallyoutwardly of the collar.
 27. A battery according to claim 26,characterized in that each seal comprises a sealing ring.
 28. A batteryaccording to claim 26, characterized in that each of the apertures ispositioned in the base of a respective recess formed in the lid, furthercomprising retaining means for each terminal that ensures that the uppersurface of the respective strap and the respective zone remain incontact and that the compression of the seal is maintained, theretaining means being positioned wholly within the recess.
 29. A batteryaccording to claim 26, characterized in that each seal is containedwithin a groove which surrounds the respective aperture.
 30. A batteryaccording to claim 29, characterized in that the groove is formed whollyin the zone formed in the underside of the lid.